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Testosterone (T) is linked with diverse characteristics of human health, yet, whether these associations reflect correlation or causation remains debated. Here, we provide a broad perspective on the role of T on complex diseases in both sexes leveraging genetic and health registry data from the UK Biobank and FinnGen (total N=625,650).We find genetically predicted T affects sex-biased and sex-specific traits, with a particularly pronounced impact on female reproductive health. We show T levels are intricately involved in metabolism, sharing many associations with sex hormone binding globulin (SHBG), but report lack of direct causality behind most of these associations. Across other disease domains, including behavior, we find little evidence for a significant contribution from normal variation in T levels. Highlighting T’s unique biology, we show T associates with antagonistic effects on stroke risk and reproduction in males and females.Overall, we underscore the involvement of T in both male and female health, and the complex mechanisms linking T levels to disease risk and sex differences.

Delayed delivery of MANF to rat brain after ischemic stroke promotes functional recovery and recruits phagocytic immune cells., Stroke is the most common cause of adult disability in developed countries, largely because spontaneous recovery is often incomplete, and no pharmacological means to hasten the recovery exist. It was recently shown that mesencephalic astrocyte–derived neurotrophic factor (MANF) induces alternative or M2 activation of immune cells after retinal damage in both fruit fly and mouse and mediates retinal repair. Therefore, we set out to study whether poststroke MANF administration would enhance brain tissue repair and affect behavioral recovery of rats after cerebral ischemic injury. We used the distal middle cerebral artery occlusion (dMCAo) model of ischemia-reperfusion injury and administered MANF either as a recombinant protein or via adeno-associated viral (AAV) vector. We discovered that, when MANF was administered to the peri-infarct region 2 or 3 days after stroke, it promoted functional recovery of the animals without affecting the lesion volume. Further, AAV7-MANF treatment transiently increased the number of phagocytic macrophages in the subcortical peri-infarct regions. In addition, the analysis of knockout mice revealed the neuroprotective effects of endogenous MANF against ischemic injury, although endogenous MANF had no effect on immune cell–related gene expression. The beneficial effect of MANF treatment on the reversal of stroke-induced behavioral deficits implies that MANF-based therapies could be used for the repair of brain tissue after stroke.